Rename flush-cache.py to flush-cache, and rearrange the code a bit.

It was working fine, but the style wasn't exactly the way I like it, because
I'm unnecessarily picky. :)

Also, removed the file extension since we should probably learn from the
fact that it's already been rewritten once from one language to another.
Who knows, maybe it will be again someday.

t/deps/basic/test.do

@@ -1,10 +1,10 @@
 rm -f *.out *.log
 
-../../flush-cache.py
+../../flush-cache
 redo-ifchange 1.out 2.out
 [ "$(cat 1.log | wc -l)" -eq 1 ] || exit 55
 [ "$(cat 2.log | wc -l)" -eq 1 ] || exit 56
-../../flush-cache.py
+../../flush-cache
 touch 1.in
 redo-ifchange 1.out 2.out
 [ "$(cat 2.log | wc -l)" -eq 1 ] || exit 58